The present invention is directed to a thermodynamic system and a method of producing work and, in particular, to such system and method having efficiency enhancing techniques.
Engine-efficiency is traditionally defined as the percentage of useful work produced by an engine divided by the heat input to the engine. In the case of complex power plants, jet engines, gasoline engines, diesel-engines, geothermal engines, etc., thermodynamic efficiency usually refers to the power-producing cycle, and plant efficiency takes into account peripheral items, such as combustor or other heat source losses and plant transmission losses beyond the immediate power-producing element. In existing state-of-the-art engine systems and power plants, the engine, thermodynamic and plant efficiencies are all in the 25 to 40 percent range mainly because existing engines and other power systems dump 60 to 75 percent of the input heat to a low temperature reservoir, such as a water stream, a cooling tower, or to the atmosphere directly.
The “Carnot Cycle” was first postulated by Sadi Carnot in 1824. Since then, this cycle has been widely used in thermodynamic analysis to determine the maximum possible engine efficiency. Here, the temperature of the input heat is given by TH, and the temperature of the output heat (to the traditional reservoir or sump) is given by TL. The low temperature reservoir, or sump, wastes such a large amount of heat in comparison to other parasitic losses, such as bearing friction and insulation heat leaks, that these later effects are often ignored in deriving the following Carnot equation:Engine efficiency=1−TL/TH  (EQ-1)
By either increasing the TH or lowering the TL, the cycle efficiency is increased. For many decades now, researchers have attempted to increase TH by adding a topping cycle, and others have attempted to decrease TL by adding a bottoming cycle.
A conventional Rankine thermodynamic system 20 (FIG. 1) includes a working fluid, such as a liquid 22, that is used at the starting point in the cycle, namely, at circled point #1. This may be at ambient conditions, but can be at conditions quite different than 1.0 atm. and 27.0 degrees centigrade. A fluid pump, such as a high pressure liquid pump 24, is then used to raise the working fluid to the desired pressure at #2. The corresponding temperature versus entropy diagram is shown in FIG. 2. Circled numbers on FIG. 2 correspond to the same circled numbers on FIG. 1. As can be seen in FIG. 2, the temperature rise across the liquid pump may be quite small. The first parcel of heat is added between points #2 and #3 in a thermal input, such as boiler 26 of FIG. 1, which represents the saturated liquid and wet region of FIG. 2. Between points #3 and #4 of both FIG. 1 and FIG. 2, the highest temperature heat is added in the super heater. Two and even three super heaters can be added to a thermodynamic system depending on the working fluid chosen and the temperature range of operation.
From points #4 and #5 on FIG. 1 and FIG. 2, a near-isentropic expansion device, such as a turbine 30, or set of cascaded turbines, or nozzle jet, or the like, produce power. Usually, the small amount of power required by the liquid pump is delivered from the power turbine. The fluid flow of the conventional Rankine thermodynamic cycle is now returned to the liquid pump, thus closing this flow loop by cooling it with a condenser 34 that exchanges heat either with water or air in contact with the ambient. This occurs between points #5 and #1, as shown on both FIG. 1 and FIG. 2. However, the thermal loop remains wide open with approximately two-thirds of the input heat being wasted between points #5 and #1.